Various types of Si epitaxial layer growing reactors have been known in the art. Example of such reactors are shown in FIGS. 1 to 3. Reactors are broadly grouped into two types, one type being a batch type for batch processing more than 2 wafers, and the other type being a sequential type for processing single wafer one after another. Batch type reactors are grouped into a vertical type (high frequency heating) shown in FIG. 1 and a barrel type (radiation heating) shown in FIG. 2, depending upon the heating method and the structure of a reaction furnace. In the case of the batch type reactor shown in FIG. 1, a plurality of semiconductor substrate wafers 4, 4, . . . are placed on a disk susceptor 2. In the case of the batch type reactor shown in FIG. 2, a plurality of wafers 4, 4, . . . are mounted on the surface of a polygon susceptor 6. An example of the reactor processing single wafer per batch is shown in FIG. 3. In the case of this reactor, a wafer 4 is placed on a disk susceptor 10 housed within a reaction vessel 8 made of a rectangular quartz tube, and radiation-heated from the top and bottom sides by halogen lamps (not shown) mounted above and below the vessel 8.
With the batch type vapor phase growing reactors shown in FIGS. 1 and 2, wafers 4 are placed on the surface of the susceptor 2, 6 side by side. As the diameter of the wafer 4 becomes large, the number of wafers which can be processed at a time greatly decreases. For example, a barrel type reactor available in markets can process at most eighteen wafers of 5 inch diameter at a time, whereas it can process fifteen wafers of 6 inch diameter, or eight wafers of 8 inch diameter. Thus, the larger the wafer diameter, the more the production performance lowers and the vapor phase grow cost increases. That is, it takes about 100 minutes to perform one cycle of epitaxial growth by conventional batch type reactor, independent of wafer diameter.
The reactor shown in FIG. 3 can shorten the vapor phase growth sequence time by one tenth the conventional time or more, although it processes one wafer at a time. The reactor can therefore improve the production performance of wafers of larger diameter. The reactor, however, uses a reaction furnace of rectangular shape. It therefore becomes necessary to set the flow rate of carrier gas (hydrogen gas) equal to or faster than a flow rate of 100 l/min or slower, which is generally the same rate as that of a conventional batch type reactor. The gas quantity per One wafer increases accordingly, so it becomes difficult to reduce the vapor phase growth cost.